The sealing units adapted to equip the rolling bearings of wheel hub assemblies are formed by so-called “packet” or “cassette” seals including a first and a second annular shields, mounted in front of each other so as to delimit an annular chamber between the shields, inside which chamber a series of sealing lips are arranged, carried by a sealing ring integrally fixed to one of the shields, generally the shield adapted in use to remain stationary. These sealing lips exert a sliding or labyrinth seal on respective sealing surfaces of the rotating shield and may have various shapes and be optionally charged by springs. An example of such a type of seal/sealing unit is given by EP0980999B1.
While they are satisfactory, the known “packet” sealing units have relatively high frictions due to the sliding lips charged by springs or in any case mounted with strong interferences. Sealing units including only labyrinth seals, in addition to being relatively large sized and complex to be implemented, have low frictions with reduced sealing efficiencies, often not sufficient for several applications, such as in the automotive field. DE102008017409 does not solve the problem.